Fluid operated circuit breaker



April 23, 1963 H. FORWALD 3,087,035

FLUID OPERATED CIRCUIT BREAKER Filed March 15, 1960 INVENTOR. Haq (M ram/J United States Patent 3,087,035 FLUID OPERATED CIRCUIT BREAKER Haakon Forwald, Lndvika, Sweden, assignor to Allmiinna Svenska Elektriska Aktiebolaget, Vasteras, Sweden, a Swedish corporation Filed Mar. 15, 1960, Ser. No. 15,201 Claims priority, application Sweden Mar. 20, 1959 6 Claims. (Cl. 200-148) This invention relates to fluid operated circuit breakers of the type wherein fluid under pressure moves the cooperable contacts of a circuit breaker to a disengaged position and retains the cooperable contacts in this disengaged position, and more specifically relates to this type of fluid operated circuit breaker wherein the operating fluid is connected to said contacts through a restric tive orifice after the contacts are disengaged to prevent loss in pressure in the event of a fluid leak.

In fluid operated circuit breakers such as air blast circuit breakers, the high pressure fluid, such as air, may be utilized in many different ways. By way of example, the air pressure may be utilized to open a main pair of contacts under load or fault conditions and when the circuit is interrupted and a series connected disconnect means is thereafter opened so that the interrupting contacts can be closed and the high pressure removed from the system with the circuit remaining isolated by the disconnect.

In other types of systems, however, the series connected disconnect is not provided so that the main interrupting contact must be retained in the disengaged position, and the high pressure air must be retained in operative relation with respect to these contacts so that they will be held open to continuously isolate the circuit.

In these types of devices, the fluid connection between the source of high pressure and the cooperating contacts may contain a leak. Accordingly, and since the high pressure is continuously maintained to hold the circuit in its open position, the leak may drain the high pressure reservoir so that the circuit will be reclosed when low pressure conditions resume, and the reservoir of operating pressure will be lost.

In accordance with the present invention, a restrictive orifice is introduced between the source of pressure and the cooperable contacts after the contacts are moved to their disengaged position whereby if there is a pressure leak between the restricted orifice and the contacts, the pressure reservoir will drain through this leak through the restricted orifice whereby pressure from the pressure reservoir is lost in a very slow manner so that corrective action may be taken before there is a complete loss in pressure.

In a typical application, the fluid operated circuit interrupter will be comprised of a plurality of series connected interrupter devices, each of which is provided with its respective fluid conductor to connect its respective contacts to the high pressure reservoir.

After the circuit is opened and maintained open by connection of the reservoir to these individual fluid conducting paths, if there is a fault in any one of the paths, this fault will be isolated from the reservoir by the orifice introduced therein and will also be isolated from the other fluid conductive paths of the other of the plurality of circuit interrupters. Accordingly the pressure maintaining the other interrupter structures disengaged will not be quickly drained through the faulty fluid conducting path so that these contacts will be retained in their disengaged position and the circuit will not be reclosed. Note that in this case each of the fluid conducting paths of each of the interrupters is provided with its own orifice which is introduced in the path responsive to circuit operation.

Accordingly, a primary object of this invention is to provide a novel safety means for fluid operated circuit breakers wherein a fluid restricting means is introduced between the fluid pressure source and the interrupter contacts to prevent draining of the pressure source in the event of a fault between the fluid conducting path to the interrupter contacts.

Another object of this invention is to prevent the draining of a high pressure fluid source in the event of a leak in the pressure system connecting the source to a pair of contacts which are operated by the fluid pressure and held disengaged by the fluid pressure.

A further object of this invention is to provide a novel safety means for preventing the rapid drain of a high pressure reservoir in the event of a leak in one of the conduits connected to the reservoir.

A further object of this invention is to limit the loss of high pressure air of a compressed air reservoir which operates the circuit breaker contacts to a disengaged position and retains the circuit breaker contacts in this disengaged position.

These and other objects of the invention will become apparent from the following description when taken in connection with the drawing which shows a typical circuit breaker which is operated by compressed air wherein the contacts are held in the open position by the compressed air after they are moved to their disengaged position.

Referring to the drawing, the circuit interrupter shown is comprised of three series connected interrupter structures 1, 2 and 3 which are connected in series with a circuit connected to terminals 4 and 5. Note that interrupter 1 is connected in series with interrupter 2 by jumper 6, while interrupter 2 is connected in series with interrupter 3 by jumper 7. The internal structure of interrupters 1, 2 and 3 includes a pair of cooperable contacts schematically illustrated as cooperable contacts 8 and 9 for interrupter 1 and may be of any standard construction. By way of example, interrupters of this type are shown in British Patent 821,069.

Clearly, the interrupter may be of any desired type wherein the contacts are operated to a disengaged position by fluid under pressure where this same fluid under pressure retains the cooperating contacts in the disengaged position. Each of interrupters 1, 2 and 3 is then carried on insulator pedestals 10, 11 and 12, respectively, in any desired manner. By way of example, the interrupters may be carried in the manner shown in British Patent 821.069.

Generally, pedestals 10, 11 and 12 are hollow and form a fluid conducting path to interrupters 1, 2 and 3 whereby the contacts of interrupters 1, 2 and 3 may be operated by pressures applied within these pedestals. The hollow pedestals 10, 11 and 12 are then connected to branch conduits 13, .14 and 15, respectively, of conduit 16. Conduit 16 is then connectable to cylinder 17 which is a source of high pressure air through the valve 18 of the pressure control means generally seen as pressure control means 19. Pressure control means 19 is comprised of a cylinder 20 which carries a piston 21 thereon. Piston 21 has an extending operating shaft which carries a valve 22 and the aforementioned valve 18 where valve 22 cooperates with a valve seat 23 to seal or exhaust the interior of conduit 16 to atmospheric pressure, while valve 18 is operable to connect or disconnect the interior of conduit 16 to the high pressure source 17. Piston 21 is biased to a normal downwardly displaced piston by compression spring 24, and the area above piston 21 is connected to the external atmosphere by aperture 25 in cylinder 20.

In order to move piston 21 upwardly, a source of control pressure (which may be derived from high pressure source 17) is connected to conduit 26 through valve 29 and then through conduit 30 which terminates below piston 21 as shown. Valve 29 is normally closed and is operable to an open position as by energizing coil 31 where valve 29 is of the electrically operable type.

If desired, coil 31 may be energized by circuits coupling the coil to the line being protected or the line connected to terminals 4 and 5 so that the valve 29 is opened responsive to predetermined fault conditions. In a like manner, valve 29 may be manually energizable for normal operation of the circuit breaker.

Responsive to energization of coil 31 and thus the opening of valve 29, the relatively high pressure of conduit 26 will be applied beneath piston 21. This will drive piston 21 upwardly against the force of biasing spring 24 whereby valve 22 closes to valve seat 23 to seal conduit 16 with respect to the external atmosphere, and valve 18 is opened to connect high pressure source 17 to the interior of conduit 16. This high pressure within conduit 16 is then applied to branch conduits 13, 14 and 15, respectively, and thus causes the movement of the contacts such as contacts 8 and 9 of conduits 1, 2 and 3 to their disengaged position. Furthermore, the contacts are held in this disengaged position by the high pressure.

In the event of a leak in any of the fluid conducting systems branching off from conduit 16, the high pressure derived from high pressure source 17 will be drained out of the system. By way of example, one of insulators 10, 11 or 12 may be damaged, and it will leak air from the undamaged interrupter branches as well as the source of compressed air 17. When the pressure reaches a sufiiciently low value because of this leak (which may happen in a relatively short time), the contacts such as contacts 8 and 9 which have been held open by this pressure will be permitted to reclose so that the circuit protected by the circuit interrupter will be closed. This, of course, can be an extremely dangerous condition and could lead to injury or death of those working on the line being protected by the interrupter and could cause serious damage or destruction of the equipment being protected by the circuit interrupter.

In accordance with the present invention, a restrictive orifice is interposed between the compressed air source 17 and each of the branch fluid conductors, whereby if any of the fluid conductors develops a pressure leak, the compressed air reservoir will be isolated from this pressure leak by the relatively restricted orifice. At the same time, the other branch insulators will similarly be isolated from the leak so that the high pressure retained in these other insulators will be operable to retain their contacts disengaged to prevent closing of the complete circuit interrupter even though one of the series connected interrupters closes.

One form of interposing orifice structure is shown in the drawing as including plungers 32, 33 and 34 which are of identical construction and are movable into the mouth of branch conduits 13, 14 and 15, respectively. The construction and operation of plungers 32, 33 and 34 is shown typically for the case of plunger 32 whereby the plunger is carried in an external housing cylinder 35 which is vented to the external atmosphere through vent 36. Plunger 32 has an extending lower bottom surface 37 .whereby the plunger 32 is operable as a piston within cylinder 35. A central opening 38 extends through plunger or piston 32 to connect its bottom piston surface to the interior of conduit 16, and the tipof plunger 32 has a small orifice 39 therein to pneumatically connect the interior of conduit 16 to the interior of branch conduit 13.

During normal operation and when valve 13 is closed and valve 22 is open, the bottom piston surface 37 of plunger 32 is connected to atmospheric pressure which is insufficient to overcome the downward biasing force of spring 40. When, however, valves 18 and 22 are moved upwardly to initiate operation of the circuit interrupter, the pressure applied to the bottom piston surface 37 of plunger 32 is sufficient to move the plunger 32 upwardly against the force of spring 46.

During the time it takes for plunger 32 to seat with respect to branch conduit 13, the pressure from reservoir 17 has been applied to interrupters 1, 2 and 3 to open their contacts and retain the contacts in this open position. Once the top of plungers 32, 33 and 34 seat with respect to branch conduits 13, 14 and 15, however, the narrow orifice such as orifice 39 is interposed between the fluid connection between the interrupters such as interrupter 1 and pressure source 17.

Assuming now that there is a leak in the branch including pedestal 13, it will be apparent that the com pressed air within this branch can drain through the leak until contacts 8 and 9 close. The pressure reservoir 17, however, is isolated from this leak, and the flow of fiuid from reservoir 17 through the leak is substantially diminished by the relatively narrow orifice 39, whereby the pressure of reservoir 17 will not be quickly exhausted.

In a like manner, the other branches including pedestals 11 and 12 will be isolated with respect to a leak in the branch including pedestal 10 by orifice 39 as well as the series connected orifice in their respective plungers 33 or 34. Thus, the contacts of interrupters 2 and 3 will not be reclosed since a substantially high pressure still remains in their branches to retain them in the open position, and the circuit will not be reclosed.

While the preferred embodiment of the invention shows plungers 32 as containing a restrictive orifice therein, the structure can be modified wherein the top of plunger 32 is completely closed. A fixed shunt pipe such as pipe 41 as shown in dotted lines for branch conduit 13 may then be connected in parallel with the sealing portion between branch conduit 13 and plunger 32.

In a like manner, parallel connected conduits having restricted openings may be provided for the other branches which include pedestals 11 and 12.

In accordance with the invention, the relative openings or cross-sectional areas of the orifices, such as orifice 39, are controlled in relation to the cross-sectional opening of the branch conduits, such as branch conduit 13, so that the flow of fluid through the orifice is cut down to any desired predetermined volume which will prevent exhausting of compressed air container 17 before some predetermined time.

Although preferred embodiments of the novel invention have been described, many variations and modifications will now be obvious to those skilled in the art, and it is preferred, therefore, to be limited not by the specific disclosure herein but only by the appended claims.

I claim:

1. In a fluid operated circuit breaker, a source of fluid under pressure, disengageable contact means movable to a circuit disengaged position responsive to fluid pressure exerted thereon, a conduit means connecting said source of pressure to said contact means, control means in said conduit means for alternately connecting the conduit means to the source to open the contact means and for connecting the main conduit means to a lower pressure to close the contact means, said conduit means otherwise being closed so as to be kept under fluid pressure so as to keep said contact means open until said control means operates to connect the conduit means to said lower pressure, and means in the conduit means between the control means and the contact means responsive to the connection or" the conduit to the source to restrict a part of the conduit means to a relatively small constantly open passage between the source and the contact means, said restricting means remaining operative as long as said conduit means is connected to said source, said last means being inoperative to restrict the conduit means when the control means connects the conduit means to said lower pressure.

2. In a device as claimed in claim 1, said fluid being a gas.

3. In a device as claimed in claim 1, said conduit means having a seat therein, said restricting means comprising a piston slidab-ly mounted in the conduit means for engagement With and disengagement from said seat, said piston having an orifice therethrough of substantially smaller cross-section than that of said conduit, and means responsive to connection of the conduit means to the source to move the piston to seat-engaging position and responsive to connection of the conduit means to said lower pressure to move the piston to seat-disengaging position.

4. In a device as claimed in claim 1, said conduit means having a seat therein, said restricting means comprising a piston slidably mounted in the conduit means for engagement with and disengagement from said seat, a bypass in the conduit means around the seat of substantially smaller cross-section than that of said conduit, and means responsive to connection of the conduit means to the source to move the piston to seat-engaging position and responsive to connection of the conduit means to said lower pressure to move the piston to scat-disengaging position.

5. In a fluid operated circuit breaker, a source of fluid under pressure, a plurality of disengageable contact means movable to a circuit disengaged position responsive to fluid pressure exerted thereon, a main conduit means connected to said source and a plurality of branch conduit means one connecting each of said contact means to the main conduit means, control means in the main conduit means for alternately connecting the main conduit means to the source to open the contact means and for connecting the main conduit means to a lower pressure to close the contact means, said main and branch conduit means being otherwise closed so as to he kept under fluid pressure so as to keep said contact means open until said control means operates to connect the conduit means to said lower pressure, and means associated with each branch conduit means responsive to the connection of the main conduit means to the source to restrict a part of the branch conduit means to a relatively small constantly open passage between the source and the contact means, said restricting means remaining operative as long as said con duit means is connected to said source, said last means being inoperative to restrict the branch conduit means when the control means connects the conduit means to said lower pressure.

6. In a device as claimed in claim 5, each branch conduit means having a seat therein, said restricting means comprising a piston for each branch conduit slidably mounted in the main conduit means for engagement with and disengagement from said seat, said piston having an orifice therethrough of substantially smaller cross-section than that of said conduit, and means responsive to connection of the conduit means to the source to move the pistons to scat-engaging position and responsive to connection of the conduit means to said lower pressure to move the pistons to seat-disengaging position.

References Cited in the file of this patent UNITED STATES PATENTS 1,477,244 Collins et a1. Dec. 11, 1923 2,472,070 Garretson June 7, 1949 2,592,079 Thommen et a1. Apr. 8, 1952 2,623,331 Greening Dec. 30, 1952 2,833,896 'Roxburgh et a1. May 6, 1958 2,864,400 Wiegel Dec. 16, 1958 2,902,570 Roxburgh et a1 Sept. 1, 1959 2,964,605 Schulz Dec. 13, 1960 FOREIGN PATENTS 133,564 Australia July 18, 1949 1,182,791 France Ian. 19, 1959 821,069 Great Britain Sept. 30, 1959 

1. IN A FLUID OPERATED CIRCUIT BREAKER, A SOURCE OF FLUID UNDER PRESSURE, DISENGAGEABLE CONTACT MEANS MOVABLE TO A CIRCUIT DISENGAGED POSITION RESPONSIVE TO FLUID PRESSURE EXERTED THEREON, A CONDUIT MEANS CONNECTING SAID SOURCE OF PRESSURE TO SAID CONTACT MEANS, CONTROL MEANS IN SAID CONDUIT MEANS FOR ALTERNATELY CONNECTING THE CONDUIT MEANS TO THE SOURCE TO OPEN THE CONTACT MEANS AND FOR CONNECTING THE MAIN CONDUIT MEANS TO A LOWER PRESSURE TO CLOSE THE CONTACT MEANS, SAID CONDUIT MEANS OTHERWISE BEING CLOSED SO AS TO BE KEPT UNDER FLUID PRESSURE SO AS TO KEEP SAID CONTACT MEANS OPEN UNTIL SAID CONTROL MEANS OPERATES TO CONNECT THE CONDUIT MEANS TO SAID LOWER PRESSURE, AND MEANS IN THE CONDUIT MEANS BETWEEN THE CONTROL MEANS AND THE CONTACT MEANS RESPONSIVE TO THE CONNECTION OF THE CONDUIT TO THE SOURCE TO RESTRICT A PART OF THE CONDUIT MEANS TO A RELATIVELY SMALL CONSTANTLY OPEN PASSAGE BETWEEN THE SOURCE AND THE CONTACT MEANS, SAID RESTRICTING MEANS REMAINING OPERATIVE AS LONG AS SAID CONDUIT MEANS IS CONNECTED TO SAID SOURCE, SAID LAST MEANS 